Oxidized Zirconium Femoral Components in Total Knee Arthroplasty: A Retrieval Study of the Tibial Bearing

Advanced materials for total knee arthroplasty, including crosslinked bearings and cobalt-chrome-molybdenum-alternative components, show promise for reducing wear rates and improving outcomes. The objective of the current study was to test whether an alternative femoral-bearing material achieved these goals.

An institutional review board-approved retrieval database was searched to identify 137 oxidized zirconium femoral total knee arthroplastycomponents from 2004 to 2023; 75 had a tibial bearing of never-irradiated polyethylene (PE) and 62 had a bearing of cross-linked polyethylene (XL). All had a polished tibial tray. The mean duration of implantation was 58 months for the PE group and 34 months for the XL group. The most common reasons for retrieval were instability and infection in the XL group and instability in the PE group. Dimensional change (creep plus wear) was measured from the thickness of the PE insert using short-duration (< 16 months) and never-implanted devices as a reference. Oxidation (maximum ketone oxidation index) was measured via fourier transform infraredusing a cross-section of the medial condyle of the PE at < three months postexplant. Statistical analyses were conducted using groups matched for in vivo duration. A P < 0.05 was considered significant.

Dimensional change rate and in vivo oxidation rate were statistically indistinguishable between the two bearing types. The mean dimensional change rate for the PE group was 0.018 ± 0.024 mm/year and 0.021 ± 0.030 mm/year for the XL group (P = 0.64). The mean oxidation rates were also not statistically different, with the mean rate for the PE group being 0.051 ± 0.052 arbitrary units (a.u.)/year and the mean value for the XL group being 0.064 ± 0.055 a.u./year (P = 0.19). Only one device (PE) exceeded the oxidation threshold, marking a decrease in mechanical properties.

The dimensional change rate and oxidation rate for tibial inserts against oxidized zirconium femoral components were low and consistent with previously reported literature values. The XL did not demonstrate superiority to PE in this analysis.